Return-Path: Received: from rly-da06.mx.aol.com (rly-da06.mail.aol.com [172.19.129.80]) by air-da07.mail.aol.com (v123.3) with ESMTP id MAILINDA072-a7149a7816d3aa; Fri, 27 Feb 2009 01:00:37 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-da06.mx.aol.com (v123.3) with ESMTP id MAILRELAYINDA061-a7149a7816d3aa; Fri, 27 Feb 2009 01:00:15 -0500 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1LcvlL-0006qv-Jm for rs_out_1@blacksheep.org; Fri, 27 Feb 2009 05:59:55 +0000 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1LcvlK-0006qm-FD for rsgb_lf_group@blacksheep.org; Fri, 27 Feb 2009 05:59:54 +0000 Received: from blu0-omc1-s9.blu0.hotmail.com ([65.55.116.20]) by relay3.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1LcvlI-0002NI-TD for rsgb_lf_group@blacksheep.org; Fri, 27 Feb 2009 05:59:54 +0000 Received: from BLU146-W13 ([65.55.116.7]) by blu0-omc1-s9.blu0.hotmail.com with Microsoft SMTPSVC(6.0.3790.3959); Thu, 26 Feb 2009 21:59:47 -0800 Message-ID: X-Originating-IP: [138.32.244.2] From: Laurence BY3A-KL1X China To: Date: Thu, 26 Feb 2009 20:59:46 -0900 Importance: Normal In-Reply-To: <2B340C0B9A8644159051241F5E7CE88F@AGB> References: <88184BDCCE244700B62ACEBF39F34582@JimPC> <2B340C0B9A8644159051241F5E7CE88F@AGB> MIME-Version: 1.0 X-OriginalArrivalTime: 27 Feb 2009 05:59:47.0331 (UTC) FILETIME=[98404D30:01C998A0] X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Content-Type: multipart/alternative; boundary="_dead58f2-f00e-4a8e-b586-f09e7868e65e_" Subject: RE: LF: Re: LF Antennas - back to basics X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=FORGED_HOTMAIL_RCVD, HTML_MESSAGE autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-AOL-IP: 193.82.116.20 X-Mailer: Unknown (No Version) --_dead58f2-f00e-4a8e-b586-f09e7868e65e_ Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Lower voltages to deal with beneath the coil too. =20 =20 > From: g8fzk@g8fzk.fsnet.co.uk > To: rsgb_lf_group@blacksheep.org > Date: Fri, 27 Feb 2009 00:19:07 +0000 > Subject: Re: LF: Re: LF Antennas - back to basics >=20 > Jim, >=20 > Yes I can confirm this :- >=20 > >>>> > increasing the height of the top loading, even if only in the middle, does > lead to substantial improvements. One benefit of doing this is that the > effective height and radiation resistance is increased by increasing the > average height of the antenna wires > >>>> >=20 > I made a substantial improvement to the original inverted L system, 35=20 > feet x 40 foot top , by adding a loading coil to the top of the vertical=20 > section (actually the 40 feet of top wire wound round a coke bottle) and=20 > providing 2 x 40 ft capacity wires 6 feet apart back to the house. >=20 > Earth is everything that conducts in the garden bonded along with a couple= =20 > of 12 ft alloy scaffold poles sunk in, to one point along with a couple=20 > of 50 foot ground lying wires as well, feed is via a auto transformer and=20= a=20 > variometer in series , I did use a parallel tuner but this flashes over=20 > above 50 watts , >=20 > A bonus , is the system now works well on 1.8 and 3.5 Mhz as well . but=20 > with a very high Q , 20 Khz qsy on 3.8 is enough for the pa to trip on vsw= r >=20 > Notably, Gary, has modelled his array , similar 35 ft vertical section,=20 > using mmana and he favours the loading coil to be placed mid section, the=20 > offset capacity section of my array dose produce a slight slew of the=20 > pattern, but nothing too radical >=20 > tnx- G .. >=20 > -------------------------------------------------- > From: "James Moritz" > Sent: Thursday, February 26, 2009 11:43 PM > To: > Subject: LF: Re: LF Antennas - back to basics >=20 > > > > Dear Andy, Dave, LF Group, > > > > My experience is that improvements to the ground system soon reach a poi= nt > > of diminishing returns where the ground connection losses are small=20 > > compared > > to other losses - I would expect you have reached that point already. In= =20 > > my > > case, literally filling the garden with wire made at best about 0.5dB > > improvement by reducing loss resistance, compared to having about 5 grou= nd > > rods spaced a few metres around the downlead and loading coil. However > > increasing the height of the top loading, even if only in the middle, do= es > > lead to substantial improvements. One benefit of doing this is that the > > effective height and radiation resistance is increased by increasing the > > average height of the antenna wires. If you are in a fairly built-up > > environment, the improvement is probably more than you would expect from > > calculating the effective height from the dimensions of the antenna=20 > > itself, > > because increasing the physical height of the antenna puts it further=20 > > above, > > or nearer the top of, screening buildings and trees etc., that are > > surrounding it. Also, moving the antenna further above loss-causing=20 > > objects > > leads to a modest reduction in the loss resistance. In my case, with an > > inverted L about 10m high at the ends and sagging to 9m in the middle, > > propping up the middle of the span with a fibreglass pole to about 14m > > increases ERP by 3 - 4dB. > > > > As to possible advantages and disadvantages of a loop compared to a > > vertical, in general the loop ought to benefit from lower dielectric=20 > > losses > > due to the generally lower voltages. The directional pattern is often > > helpful on receive. But the figure-of-eight directional pattern could al= so > > be a drawback for a transmit antenna where it isn't practical to rotate=20 > > the > > antenna to avoid having nulls in awkward directions. Also, one has to=20 > > think > > about the scale. AA1A's loop is quite big in overall dimensions compared= =20 > > to > > G4JNT's vertical. The radiation resistance of a loop is proportional to=20 > > the > > square of the area, which is proportional to the square of the linear > > dimensions of the loop conductor - so when scaling down a loop, one woul= d > > expect Rrad to reduce much faster than Rloss due to reduction in=20 > > perimeter, > > and so efficiency of relatively small loops to be poor. > > > > Cheers, Jim Moritz > > 73 de M0BMU > > > > ----- Original Message -----=20 > > From: "Andy Talbot" > > To: > > Sent: Thursday, February 26, 2009 4:16 PM > > Subject: LF: LF Antennas - back to basics > > > > > >> Firstly, bearing in mind there is no scope whatsoever to raise one end > >> of the capacity hat which is defined by the apex of the house roof, > >> and the other end would also need some major sugery to raise its heigh > >> substantially, that only leaves the middle, ie the height of the > >> actual radiator. It wouldn't be too difficult to raise this to 10m > >> or even more with a fibreglass pole, but will I be throwing away all > >> the advantage by having the top-hat drooping down to 7m? > >> > >> Secondly, pictures of other peoples antennas aften show a substantial > >> grounding plate immediately under and around the antenna base. Just > >> how far out is is worth going with a really substantial base. I > >> could cut more conductors into the ground; while the ground is still > >> is still soggy in March may be a good time to do this. > >> > >> Any ideas please ...? > >> > >> > >> Andy G4JNT > >> www.g4jnt.com > >> > > > > > > >=20 >=20 >=20 > > > > No virus found in this incoming message. > > Checked by AVG - www.avg.com > > Version: 8.0.237 / Virus Database: 270.11.3/1974 - Release Date: 02/26/0= 9=20 > > 14:51:00 > >=20 >=20 >=20 _________________________________________________________________ Windows Live=99: Discover 10 secrets about the new Windows Live. =20 http://windowslive.com/connect/post/jamiethomson.spaces.live.com-Blog-cns!55= 0F681DAD532637!7540.entry?ocid=3DTXT_TAGLM_WL_t2_ugc_post_022009=3D --_dead58f2-f00e-4a8e-b586-f09e7868e65e_ Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Lower voltages to deal with beneath the coil too.
 

 
> From: g8fzk@g8fzk.fsnet.co.uk
> To: rsgb_lf_group@b= lacksheep.org
> Date: Fri, 27 Feb 2009 00:19:07 +0000
> Subject:= Re: LF: Re: LF Antennas - back to basics
>
> Jim,
>
= > Yes I can confirm this :-
>
> >>>>
> inc= reasing the height of the top loading, even if only in the middle, does
&= gt; lead to substantial improvements. One benefit of doing this is that the<= BR>> effective height and radiation resistance is increased by increasing= the
> average height of the antenna wires
> >>>>>
> I made a substantial improvement to the original inverted L s= ystem, 35
> feet x 40 foot top , by adding a loading coil to the top=20= of the vertical
> section (actually the 40 feet of top wire wound rou= nd a coke bottle) and
> providing 2 x 40 ft capacity wires 6 feet apa= rt back to the house.
>
> Earth is everything that conducts in=20= the garden bonded along with a couple
> of 12 ft alloy scaffold poles= sunk in, to one point along with a couple
> of 50 foot ground lying=20= wires as well, feed is via a auto transformer and a
> variometer in s= eries , I did use a parallel tuner but this flashes over
> above 50 w= atts ,
>
> A bonus , is the system now works well on 1.8 and 3.= 5 Mhz as well . but
> with a very high Q , 20 Khz qsy on 3.8 is enoug= h for the pa to trip on vswr
>
> Notably, Gary, has modelled hi= s array , similar 35 ft vertical section,
> using mmana and he favour= s the loading coil to be placed mid section, the
> offset capacity se= ction of my array dose produce a slight slew of the
> pattern, but no= thing too radical
>
> tnx- G ..
>
> --------------= ------------------------------------
> From: "James Moritz" <james.= moritz@btopenworld.com>
> Sent: Thursday, February 26, 2009 11:43 P= M
> To: <rsgb_lf_group@blacksheep.org>
> Subject: LF: Re:=20= LF Antennas - back to basics
>
> >
> > Dear Andy, D= ave, LF Group,
> >
> > My experience is that improvements=20= to the ground system soon reach a point
> > of diminishing returns=20= where the ground connection losses are small
> > compared
>=20= > to other losses - I would expect you have reached that point already. I= n
> > my
> > case, literally filling the garden with wire= made at best about 0.5dB
> > improvement by reducing loss resistan= ce, compared to having about 5 ground
> > rods spaced a few metres=20= around the downlead and loading coil. However
> > increasing the he= ight of the top loading, even if only in the middle, does
> > lead=20= to substantial improvements. One benefit of doing this is that the
> &= gt; effective height and radiation resistance is increased by increasing the=
> > average height of the antenna wires. If you are in a fairly bu= ilt-up
> > environment, the improvement is probably more than you w= ould expect from
> > calculating the effective height from the dime= nsions of the antenna
> > itself,
> > because increasing=20= the physical height of the antenna puts it further
> > above,
&= gt; > or nearer the top of, screening buildings and trees etc., that are<= BR>> > surrounding it. Also, moving the antenna further above loss-cau= sing
> > objects
> > leads to a modest reduction in the l= oss resistance. In my case, with an
> > inverted L about 10m high a= t the ends and sagging to 9m in the middle,
> > propping up the mid= dle of the span with a fibreglass pole to about 14m
> > increases E= RP by 3 - 4dB.
> >
> > As to possible advantages and disad= vantages of a loop compared to a
> > vertical, in general the loop=20= ought to benefit from lower dielectric
> > losses
> > due= to the generally lower voltages. The directional pattern is often
> &= gt; helpful on receive. But the figure-of-eight directional pattern could al= so
> > be a drawback for a transmit antenna where it isn't practica= l to rotate
> > the
> > antenna to avoid having nulls in=20= awkward directions. Also, one has to
> > think
> > about=20= the scale. AA1A's loop is quite big in overall dimensions compared
>=20= > to
> > G4JNT's vertical. The radiation resistance of a loop is= proportional to
> > the
> > square of the area, which is= proportional to the square of the linear
> > dimensions of the loo= p conductor - so when scaling down a loop, one would
> > expect Rra= d to reduce much faster than Rloss due to reduction in
> > perimet= er,
> > and so efficiency of relatively small loops to be poor.
= > >
> > Cheers, Jim Moritz
> > 73 de M0BMU
> &= gt;
> > ----- Original Message -----
> > From: "Andy Talb= ot" <andy.g4jnt@googlemail.com>
> > To: <rsgb_lf_group@bla= cksheep.org>
> > Sent: Thursday, February 26, 2009 4:16 PM
&g= t; > Subject: LF: LF Antennas - back to basics
> >
> ><= BR>> >> Firstly, bearing in mind there is no scope whatsoever to ra= ise one end
> >> of the capacity hat which is defined by the ape= x of the house roof,
> >> and the other end would also need some= major sugery to raise its heigh
> >> substantially, that only l= eaves the middle, ie the height of the
> >> actual radiator. It=20= wouldn't be too difficult to raise this to 10m
> >> or even more= with a fibreglass pole, but will I be throwing away all
> >> th= e advantage by having the top-hat drooping down to 7m?
> >>
&= gt; >> Secondly, pictures of other peoples antennas aften show a subst= antial
> >> grounding plate immediately under and around the ant= enna base. Just
> >> how far out is is worth going with a really= substantial base. I
> >> could cut more conductors into the gro= und; while the ground is still
> >> is still soggy in March may=20= be a good time to do this.
> >>
> >> Any ideas pleas= e ...?
> >>
> >>
> >> Andy G4JNT
>= >> www.g4jnt.com
> >>
> >
> >
> &= gt;
>
>
>
> >
> > No virus found in t= his incoming message.
> > Checked by AVG - www..avg.com
> >= ; Version: 8.0.237 / Virus Database: 270.11.3/1974 - Release Date: 02/26/09=20=
> > 14:51:00
> >
>
>

Window= s Live=99: Discover 10 secrets about the new Windows Live. View post. =3D --_dead58f2-f00e-4a8e-b586-f09e7868e65e_--